descriptive error message when AR adapter was not found. Closes #7313.

1 files changed, 5 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/connection_specification.rb b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
index 577a362568..873f1ad3d4 100644
--- a/activerecord/lib/active_record/connection_adapters/connection_specification.rb
+++ b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
@@ -51,10 +51,13 @@ module ActiveRecord
 
           raise(AdapterNotSpecified, "database configuration does not specify adapter") unless spec.key?(:adapter)
 
+          path_to_adapter = "active_record/connection_adapters/#{spec[:adapter]}_adapter"
           begin
-            require "active_record/connection_adapters/#{spec[:adapter]}_adapter"
+            require path_to_adapter
+          rescue Gem::LoadError => e
+            raise Gem::LoadError, "Specified '#{spec[:adapter]}' for database adapter, but the gem is not loaded. Add `gem '#{e.name}'` to your Gemfile."
           rescue LoadError => e
-            raise LoadError, "Please install the #{spec[:adapter]} adapter: `gem install activerecord-#{spec[:adapter]}-adapter` (#{e.message})", e.backtrace
+            raise LoadError, "Could not load '#{path_to_adapter}'. Make sure that the adapter in config/database.yml is valid. If you use an adapter other than 'mysql', 'mysql2', 'postgresql' or 'sqlite3' add the necessary adapter gem to the Gemfile.", e.backtrace
           end
 
           adapter_method = "#{spec[:adapter]}_connection"